Acoustic emission toughness testing for PDC, PCBN, or other hard or superhard materials

ABSTRACT

An acoustic emissions testing device includes a rock sample including a first surface, an acoustic sensor, an indenter coupled to the first surface, and a load. The load is exerted on the indenter, which transfers the load to the first surface. The acoustic sensor is communicably coupled to the rock sample and detects one or more acoustic events occurring within the rock sample. An acoustic emissions testing system includes a data recorder coupled to the testing device. The data recorder records the data from testing device. Based upon the data received, the toughness of the sample is objectively determined and can be ranked comparatively to the toughness of other samples. The load is ramped up to a peak load, held for a period of time, and then ramped down.

RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patent application Ser. No. 12/754,784, entitled “Acoustic Emission Toughness Testing For PDC, PCBN, Or Other Hard Or Superhard Material Inserts” and filed on Apr. 6, 2010, which is hereby incorporated by reference.

The present application is related to U.S. patent application Ser. No. 12/754,738, entitled “Acoustic Emission Toughness Testing For PDC, PCBN, Or Other Hard Or Superhard Material Inserts” and filed on Apr. 6, 2010, which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to a method, apparatus, and software for testing the intrinsic strength, or toughness, of hard or superhard materials; and more particularly, to a method, apparatus, and software for testing the intrinsic strength, or toughness, of hard or superhard materials using acoustic emissions.

BACKGROUND

FIG. 1 shows a superhard material 100 that is insertable within a downhole tool (not shown), such as a drill bit or a reamer, in accordance with an exemplary embodiment of the invention. One example of a superhard material 100 is a cutting element 100, or cutter or insert, for rock bits, as shown in FIG. 1. However, the superhard material 100 can be formed into other structures based upon the application that it is to be used in. The cutting element 100 typically includes a substrate 110 having a contact face 115 and a cutting table 120. The cutting table 120 is fabricated using an ultra hard layer which is bonded to the contact face 115 by a sintering process according to one example. According to some examples, the substrate 110 is generally made from tungsten carbide-cobalt, or tungsten carbide, while the cutting table 120 is formed using a polycrystalline ultra hard material layer, such as polycrystalline diamond (“PCD”) or polycrystalline cubic boron nitride (“PCBN”). These cutting elements 100 are fabricated according to processes and materials known to persons having ordinary skill in the art. Although the cutting table 120 is shown having a substantially planar outer surface, the cutting table 120 can have alternative shaped outer surfaces, such as dome-shaped, concave-shaped, or other non-planar shaped outer surfaces, in other embodiments. Although some exemplary formulations for the cutting element 100 have been provided, other formulations and structures known to people having ordinary skill in the art can be used depending upon the application. Although rock drilling is one application that the superhard material 100 can be used in and which is described hereinbelow, the superhard material 100 can be used in various other applications including, but not limited to, machining, woodworking, and quarrying.

Different PCD, PCBN, hard, and superhard material grades are available for the cutters 100 to be used in various applications, such as drilling different rock formations using different drill bit designs or machining different metals or materials. Common problems associated with these cutters 100 include chipping, spalling, partial fracturing, cracking, and/or flaking of the cutting table 120 during use. These problems result in the early failure of the cutting table 120 and/or the substrate 110. Typically, high magnitude stresses generated on the cutting table 120 at the region where the cutting table 120 makes contact with earthen formations during drilling can cause these problems. These problems increase the cost of drilling due to costs associated with repair, production downtime, and labor costs. Thus, an end-user, such as a bit designer or a field application engineer, chooses the best performing grade of the cutter 100 for any given drilling or machining task to reduce these common problems from occurring. For example, the end-user selects an appropriate cutter 100 by balancing the wear resistance and the impact resistance of the cutter 100, as determined using conventional methods. Typically, the information available to the end-user for selecting the appropriate grade cutter 100 for a particular application is derived from historical data records that show performance of different grades of PCD, PCBN, hard, or superhard material in specific areas and/or from laboratory functional tests which attempt to mimic various drilling or machining conditions while testing different cutters 100. There are currently two main categories of laboratory functional testing that are used in the drilling industry. These tests are the wear abrasion test and the impact test.

Superhard materials 100, which include polycrystalline diamond compact (“PDC”) cutters 100, have been tested for abrasive wear resistance through the use of two conventional testing methods. The PDC cutter 100 includes the cutting table 120 fabricated from PCD. FIG. 2 shows a lathe 200 for testing abrasive wear resistance using a conventional granite log test. Although one exemplary apparatus configuration for the lathe 200 is provided, other apparatus configurations known to people having ordinary skill in the art can be used without departing from the scope and spirit of the exemplary embodiment.

Referring to FIG. 2, the lathe 200 includes a chuck 210, a tailstock 220, and a tool post 230 positioned between the chuck 210 and the tailstock 220. A target cylinder 250 has a first end 252, a second end 254, and a sidewall 258 extending from the first end 252 to the second end 254. According to the conventional granite log test, sidewall 258 is an exposed surface 259 which makes contact with the superhard component 100 during the test. The first end 252 is coupled to the chuck 210, while the second end 254 is coupled to the tailstock 220. The chuck 210 is configured to rotate, thereby causing the target cylinder 250 to also rotate along a central axis 256 of the target cylinder 250. The tailstock 220 is configured to hold the second end 254 in place while the target cylinder 250 rotates. The target cylinder 250 is fabricated from a single uniform material, which is typically granite. However, other rock types have been used for the target cylinder 250, which includes, but is not limited to, Jackforck sandstone, Indiana limestone, Berea sandstone, Carthage marble, Champlain black marble, Berkley granite, Sierra white granite, Texas pink granite, and Georgia gray granite.

The PDC cutter 100 is fitted to the lathe's tool post 230 so that the PDC cutter 100 makes contact with the target cylinder's 250 exposed surface 259 and drawn back and forth across the exposed surface 259. The tool post 230 has an inward feed rate on the target cylinder 250. The abrasive wear resistance for the PDC cutter 100 is determined as a wear ratio, which is defined as the volume of target cylinder 250 that is removed to the volume of the PDC cutter 100 that is removed. Alternatively, instead of measuring volume, the distance that the PDC cutter 100 travels across the target cylinder 250 can be measured and used to quantify the abrasive wear resistance for the PDC cutter 100. Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the wear resistance using the granite log test. Operation and construction of the lathe 200 is known to people having ordinary skill in the art. Descriptions of this type of test is found in the Eaton, B. A., Bower, Jr., A. B., and Martis, J. A. “Manufactured Diamond Cutters Used In Drilling Bits.” Journal of Petroleum Technology, May 1975, 543-551. Society of Petroleum Engineers paper 5074-PA, which was published in the Journal of Petroleum Technology in May 1975, and also found in Maurer, William C., Advanced Drilling Techniques, Chapter 22, The Petroleum Publishing Company, 1980, pp. 541-591, which is incorporated by reference herein.

FIG. 3 shows a vertical boring mill 300 for testing abrasive wear resistance using a vertical boring mill (“VBM”) test or vertical turret lathe (“VTL”) test. Although one exemplary apparatus configuration for the VBM 300 is provided, other apparatus configurations can be used without departing from the scope and spirit of the exemplary embodiment. The vertical boring mill 300 includes a rotating table 310 and a tool holder 320 positioned above the rotating table 310. A target cylinder 350 has a first end 352, a second end 354, and a sidewall 358 extending from the first end 352 to the second end 354. According to the conventional VBM test, second end 354 is an exposed surface 359 which makes contact with a superhard material 100 during the test. The target cylinder 350 is typically about thirty inches to about sixty inches in diameter; however, this diameter can be greater or smaller.

The first end 352 is mounted on the lower rotating table 310 of the VBM 300, thereby having the exposed surface 359 face the tool holder 320. The PDC cutter 100 is mounted in the tool holder 320 above the target cylinder's exposed surface 359 and makes contact with the exposed surface 359. The target cylinder 350 is rotated as the tool holder 320 cycles the PDC cutter 100 from the center of the target cylinder's exposed surface 359 out to its edge and back again to the center of the target cylinder's exposed surface 359. The tool holder 320 has a predetermined downward feed rate. The VBM method allows for higher loads to be placed on the PDC cutter 100 and the larger target cylinder 350 provides for a greater rock volume for the PDC cutter 100 to act on. The target cylinder 350 is typically fabricated from granite; however, the target cylinder can be fabricated from other materials that include, but is not limited to, Jackforck sandstone, Indiana limestone, Berea sandstone, Carthage marble, Champlain black marble, Berkley granite, Sierra white granite, Texas pink granite, and Georgia gray granite.

The abrasive wear resistance for the PDC cutter 100 is determined as a wear ratio, which is defined as the volume of target cylinder 350 that is removed to the volume of the PDC cutter 100 that is removed. Alternatively, instead of measuring volume, the distance that the PDC cutter 100 travels across the target cylinder 350 can be measured and used to quantify the abrasive wear resistance for the PDC cutter 100. Alternatively, other methods known to persons having ordinary skill in the art can be used to determine the wear resistance using the VBM test. Operation and construction of the VBM 300 is known to people having ordinary skill in the art. A description for this type of testing can be found in Bertagnolli, Ken and Vale, Roger, “Understanding and Controlling Residual Stresses in Thick Polycrystalline Diamond Cutters for Enhanced Durability,” US Synthetic Corporation, 2000, which is incorporated by reference in its entirety herein.

In addition to testing for abrasive wear resistance, PDC cutters 100 also can be tested for resistance to impact loading. FIG. 4 shows a drop tower apparatus 400 for testing impact resistance of superhard components using a “drop hammer” test where a metal weight 450 is suspended above and dropped onto the cutter 100. The “drop hammer” test attempts to emulate the type of loading that can be encountered when the PDC cutter 100 transitions from one formation to another or experiences lateral and axial vibrations. Results from the impact testing allows for ranking different cutters based upon their impact strength; however, these ranking do not allow for predictions to be made according to how the cutters 100 will perform in the actual field.

Referring to FIG. 4, the drop tower apparatus 400 includes a superhard material 100, such as a PDC cutter, a target fixture 420, and a strike plate 450 positioned above the superhard material 100. The PDC cutter 100 is locked into the target fixture 420. The strike plate 450, or weight, is typically fabricated from steel and is positioned above the PDC cutter 100. However, the strike plate 450 can be fabricated from alternative materials known to persons having ordinary skill in the art. The PDC cutter 100 is typically held at a backrake angle 415 with the diamond table 120 of the PDC cutter 100 angled upward towards the strike plate 450. The range for the backrake angle 415 is known to people having ordinary skill in the art.

The strike plate 450 is repeatedly dropped down on the edge of the PDC cutter 100 until the edge of the PDC cutter 100 breaks away or spalls off. These tests are also referred to as “side impact” tests because the strike plate 450 impacts an exposed edge of the diamond table 120. Failures typically appear in either the diamond table 120 or at the contact face 115 between the diamond table 120 and the carbide substrate 110. The “drop hammer” test is very sensitive to the edge geometry of the diamond table 120. If the table 120 is slightly chamfered, the test results can be altered considerably. The total energy, expressed in Joules, expended to make the initial fracture in the diamond table 120 is recorded. For more highly impact resistant cutters 100, the strike plate 450 can be dropped according to a preset plan from increasing heights to impart greater impact energy on the cutter 100 to achieve failure. However, this “drop hammer” test embodies drawbacks in that this method requires that many cutters 100 be tested to achieve a valid statistical sampling that can compare the relative impact resistance of one cutter type to another cutter type. The test is inadequate in providing results that reflect the true impact resistance of the entire cutter 100 as it would see impact loads in a downhole environment. The test exhibits a static impact effect whereas the true impact is dynamic. The number of impacts per second can be as high as 100 hertz (“Hz”). Also, the amount of damage to the cutter is subjectively evaluated by someone with a trained eye and is compared to damages incurred by other cutters.

While the results for different wear tests available in the market have generally a reasonable degree of agreement with the actual field performance, the same is not the case for the results of conventional impact tests. Although there is some degree of correlation between the results of conventional impact tests and actual field performance, the scattering of the data is usually very large, thereby causing predictions on how cutters will behave in actual field performance to be difficult and/or inaccurate. Also, many fractures occurring within the cutter are not detected using these conventional tests and therefore go undetected when evaluating the toughness of the cutter.

Additionally, since the bit selection is a critical process, it is important to know the mechanical properties of the different rocks the bit is to drill through. One of the most important parameters currently used for the bit selection is the unconfined compressive strength (“UCS”) of the rock, which can be measured directly on core samples or evaluated indirectly from log data. However, the UCS of the rock should not be solely relied on when selecting the bit because the UCS can be misleading, especially when the rock UCS is greater than 15000 psi and is brittle, thereby having a low fracture toughness K_(1C). Thus, fracture toughness of the rock should also be considered when selecting the proper drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the invention are best understood with reference to the following description of certain exemplary embodiments, when read in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a superhard material that is insertable within a downhole tool in accordance with an exemplary embodiment of the invention;

FIG. 2 shows a lathe for testing abrasive wear resistance using a conventional granite log test;

FIG. 3 shows a vertical boring mill for testing abrasive wear resistance using a vertical boring mill test or vertical turret lathe test;

FIG. 4 shows a drop tower apparatus for testing impact resistance of superhard components using a “drop hammer” test;

FIG. 5 shows a perspective view of an acoustic emission testing system in accordance with an exemplary embodiment of the present invention;

FIG. 6 shows a cross-sectional view of the acoustic emission testing device of FIG. 5 in accordance with an exemplary embodiment of the present invention;

FIG. 7 shows a perspective view of a cutter holder, as shown in FIG. 5, in accordance with an exemplary embodiment of the present invention;

FIG. 8 shows a perspective view of the acoustic emission testing device of FIG. 5 with the indenter being removed from the cutter holder in accordance with an exemplary embodiment of the present invention;

FIG. 9 shows a perspective view of an acoustic emission testing system in accordance with an alternative exemplary embodiment of the present invention;

FIG. 10 shows a schematic block diagram of a data recorder of FIG. 5 in accordance with an exemplary embodiment;

FIG. 11 shows a graphical cutter acoustic emission and loading representation for a cutter experiencing a load of up to about two kilonewtons in accordance with an exemplary embodiment of the present invention;

FIG. 12 shows a graphical cutter acoustic emission and loading representation for a cutter experiencing a load of up to about five kilonewtons in accordance with an exemplary embodiment of the present invention;

FIG. 13 shows a graphical cutter acoustic emission and loading representation for a cutter experiencing a load of up to about thirty kilonewtons in accordance with an exemplary embodiment of the present invention;

FIG. 14 shows a graphical cutter acoustic emission and loading representation for a cutter experiencing a load of up to about forty kilonewtons in accordance with an exemplary embodiment of the present invention;

FIG. 15A shows a graphical cutter acoustic emission and loading representation for a cutter manufacturer #1 cutter sample #1 cutter type experiencing a load of up to about forty-five kilonewtons in accordance with an exemplary embodiment of the present invention;

FIG. 15B shows a graphical cutter acoustic emission and loading representation for a cutter manufacturer #2 cutter sample #2 cutter type experiencing a load of up to about thirty kilonewtons in accordance with an exemplary embodiment of the present invention;

FIG. 16 illustrates a flowchart of a method for analyzing data points received from the acoustic sensor, wherein the method includes a loop one method and a loop two method in accordance with an exemplary embodiment of the present invention;

FIG. 17 illustrates a detailed flowchart of the loop one method of FIG. 16 in accordance with an exemplary embodiment of the present invention;

FIG. 18 illustrates a detailed flowchart of the loop two method of FIG. 16 in accordance with an exemplary embodiment of the present invention;

FIG. 19 shows a graphical cutter acoustic emission representation for a cutter experiencing a load in accordance with an exemplary embodiment of the present invention;

FIG. 20 shows a magnified view of a portion of a graphical cutter acoustic emission representation for a cutter experiencing a load in accordance with an exemplary embodiment of the present invention;

FIG. 21 shows a cumulative distribution representation for each actual acoustic event in accordance with an exemplary embodiment of the present invention;

FIG. 22 shows a block diagram of the processor of FIG. 10 in accordance with an exemplary embodiment;

FIG. 23 shows a rock sample that is testable within the acoustic emission testing systems of FIGS. 5 and 9, respectively, in lieu of the cutter of FIG. 1 in accordance with an exemplary embodiment; and

FIG. 24 shows the acoustic emission testing device of FIG. 5 inserted within a pressurizable chamber in accordance with an exemplary embodiment.

The drawings illustrate only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments.

BRIEF DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention is directed to a method, apparatus, and software for testing the intrinsic strength, or toughness, of hard or superhard materials using acoustic emissions. Although the description of exemplary embodiments is provided below in conjunction with a PDC cutter, alternate embodiments of the invention may be applicable to other types of hard or superhard materials including, but not limited to, PCBN cutters, rock samples, or other hard or superhard materials known or not yet known to persons having ordinary skill in the art. For example, the hard or superhard materials include cemented tungsten carbide, silicon carbide, tungsten carbide matrix coupons, ceramics, or chemical vapor deposition (“CVD”) coated inserts. The hard or superhard materials also include rock samples that include, but are not limited to, hard rock samples and/or cemented rock samples obtained from a drill hole.

The invention is better understood by reading the following description of non-limiting, exemplary embodiments with reference to the attached drawings, wherein like parts of each of the figures are identified by like reference characters, and which are briefly described as follows. FIG. 5 shows a perspective view of an acoustic emission testing system 500 in accordance with an exemplary embodiment of the present invention. FIG. 6 shows a cross-sectional view of the acoustic emission testing device 505 of FIG. 5 in accordance with an exemplary embodiment of the present invention. Referring to FIGS. 5 and 6, the acoustic emission testing system 500 includes an acoustic emission testing device 505 communicably coupled to a data recorder 590. The acoustic emission testing device 505 includes a cutter holder 510, the cutter 100, an indenter 550, and an acoustic sensor 570. In certain embodiments, however, the cutter holder 510 is optional. Although the cutter 100 is depicted in the exemplary embodiment, a rock sample 2300 (FIG. 23) replaces the cutter 100 in alternative exemplary embodiments.

FIG. 7 shows a perspective view of the cutter holder 510 in accordance with an exemplary embodiment of the present invention. Referring to FIGS. 5, 6, and 7, the cutter holder 510 includes first surface 712, a second surface 714, and a side surface 716. The first surface 712 is disposed in a plane that is substantially parallel to the plane that the second surface 714 is disposed. The side surface 716 extends from the first surface 712 to the second surface 714. According to some exemplary embodiments, the side surface 716 is substantially perpendicular to at least one of the first surface 712 and the second surface 714. According to alternative exemplary embodiments, the side surface 716 is not substantially perpendicular to either the first surface 712 or the second surface 714. The cutter holder 510 is fabricated from steel; however, according to other exemplary embodiments, the cutter holder 510 is fabricated from any metal, wood, or other suitable material known to people having ordinary skill in the art that is capable of withstanding a load 580, which is described in further detail below, that is to be applied. The load 580 can range from about zero kilonewtons to about seventy kilonewtons. In certain exemplary embodiments, the suitable material is capable of being machined or molded and is capable of propagating sound. In certain exemplary embodiments, the suitable material is capable of propagating sound at a speed of about 1/kilometers per second or higher.

The cutter holder 510 is shaped in a substantially cylindrical shape, wherein the first surface 712 is substantially circular shaped, the second surface is substantially circular shaped, and the side surface 716 is substantially arcuate shaped. However, the side surface 716 includes a coupling portion 730, which is substantially planar, or flat-surfaced, and extends from the first surface 712 to the second surface 714. The coupling portion 730 provides a surface for coupling the acoustic sensor 570 to the cutter holder 510. In certain exemplary embodiments, the coupling portion 730 does not extend the entire length from the first surface 712 to the second surface 714. In some exemplary embodiments, the acoustic sensor 570 is sized such that the acoustic sensor 570 is able to be coupled to the side surface 716 that is arcuate shaped. Thus, the coupling portion 730 is optional in those exemplary embodiments. Although one exemplary shape is provided for the cutter holder 510, the cutter holder 510 can be shaped into any other geometric or non-geometric shape, such as square shaped cylinder or triangular shaped cylinder, without departing from the scope and spirit of the exemplary embodiment.

A cavity 720 is formed within the cutter holder 510 and is sized to receive the cutter 100, or some other hard or superhard material such as a rock sample 2300 (FIG. 23), which is further described below. The cavity 720 is sized slightly larger in diameter than the diameter of the cutter 100, thereby allowing the cutter 100 to easily and freely fit within the cavity 720. The cavity 720 extends from the first surface 712 towards the second surface 714, but does not reach the second surface 714. In other exemplary embodiments, the cavity 720 extends from the first surface 712 to the second surface 714 and proceeds through the cutter holder 510, thereby forming a hole within the cutter holder 510. The cavity 720 is circular in shape, but is any other geometric or non-geometric shape in other exemplary embodiments. The cavity 720 is formed by machining the cutter holder 510 or molding the cutter holder 510 to have the cavity 720 formed therein. Alternatively, the cavity 720 is formed using other methods known to people having ordinary skill in the art. In certain exemplary embodiments, the cavity 720 is formed in a manner to ensure that the cutter 100 is properly aligned in the same manner each time the cutter 100 is inserted within the cavity 720.

The cutter 100 has been previously described with respect to FIG. 1 and is applicable to the exemplary embodiments. Briefly, the cutter 100 includes the substrate 110 and the cutter table 120, which is formed or coupled to the top of the substrate 110. In the exemplary embodiment, the cutter table 120 is formed from PCD, but alternative exemplary embodiments have the cutter table 120 fabricated from other materials, such as PCBN, without departing from the scope and spirit of the exemplary embodiment. Although cutter 100 has a planar cutter table 120, or is flat-faced, the cutter table 120 can be dome shaped, concave shaped, or any other shape known to people having ordinary skill in the art.

The cutter 100 includes finished and/or grounded cutters as well as “raw” cutters. “Raw” cutters are unfinished and are cutters that are typically available right out of a pressing cell. Embodiments of the present invention allow testing of both these cutter types. Since cutter manufacturers are able to test “raw” cutters in accordance with embodiments of the present invention, cutter manufacturers are able to insure that they are meeting specification early in a cutter production run. If cutter manufacturers determine that the “raw” cutters 100 are not meeting appropriate specifications, they are able to make the necessary changes in their operating parameters to get “good” cutters before continuing on with the cutter production run. Additionally, “raw” cutters are capable of being tested at a lower kilonewton level, or load, to insure that the “raw” cutters are not cracking under the given load. If cracks are occurring during the testing of the “raw” cutters, cutter manufacturers can forgo the additional expenses associated with finishing and grinding these “raw” cutters; thereby saving unnecessary cost expenditures. Hence, each “raw” cutter is capable of being tested through the acoustic emission testing system 500 using lower load levels to insure that the cutters 100 are “good” cutters.

Referring to FIG. 6, the cutter 100 is inserted within the cavity 720 of the cutter holder 510. The cutter 100 is oriented within the cavity 720 so that the cutter table 120 is facing towards the first surface 712, or away from the second surface 714. According to this exemplary embodiment, the entire cutter 100 is inserted within the cavity 720. However, in alternative exemplary embodiments, a portion of the cutter 100, which includes the entire substrate 110, is completely inserted within the cavity 720. Thus, in these alternative exemplary embodiments, at least a portion of the cutter table 120 is not inserted within the cavity 720. Once the cutter 100 has been inserted within the cavity 720, an air gap 610 is formed between the outer perimeter of the cutter 100 and the outer surface of the cavity 720. According to certain exemplary embodiments, a lubricant 620 is applied to the outer perimeter of the cutter 100 or placed within the cavity 720. In these exemplary embodiments, once the cutter 100 is placed within the cavity 720, the lubricant 620 fills at least a portion of the air gap 610 such that the lubricant 620 adheres to both the outer surface of the cavity 720 and the outer perimeter of the cutter 100 and occupies the portion of the air gap 610 therebetween. In other exemplary embodiments, the lubricant 620 is placed at least between the bottom surface of the cavity 720 and the base of the cutter 100. The lubricant 620 improves acoustic transmission between the cutter 100 and the acoustic sensor 570. The lubricant 620 is a gel, such as an ultrasound gel, according to some exemplary embodiments. However, in alternative exemplary embodiments, other materials can be used as the lubricant 620, which includes, but is not limited to, oils, grease, and lotions. These materials are capable of being spread, adhering to surfaces, and not rapidly drying out. Although the cutter 100 is described as being used in this exemplary embodiment, other hard or superhard materials that desire a toughness testing can be used in lieu of the cutter 100.

Referring back to FIGS. 5 and 6, the indenter 550 is dome shaped at a first end 650 and has a planar surface at a second end 652. The indenter 550 is fabricated to be tougher than the cutter 100 so that once load 580 is applied to the indenter 550, it is the cutter 100 that is damaged and not the indenter 550. For example, the indenter 550 is fabricated from tungsten carbide-cobalt; however, other materials known to those having ordinary skill in the art can be used to fabricate the indenter 550. In certain exemplary embodiments, the cobalt content of the indenter 550 ranges from about six percent to about twenty percent. In certain exemplary embodiments, the cobalt content of the indenter 550 is greater than the cobalt content of the cutter table 120 of the cutter 100. Additionally, in certain exemplary embodiments, a PCD layer is formed or mounted onto the first end 650 of the indenter 550. In these embodiments, the cobalt content of the PCD layer of the indenter 550 is greater than the cobalt content of the cutter table 120 of the cutter 100. Also, in these exemplary embodiments, the cobalt content of the PCD layer of the indenter 550 ranges from about six percent to about twenty percent. Although cobalt is used in these exemplary embodiments to make the indenter tougher than the cutter 100, other components known to people having ordinary skill in the art can be used in alternative exemplary embodiments.

The indenter 550 is sized to fit within the cavity 720 so that it makes contact with the cutter 100. In certain exemplary embodiments, the perimeter of the indenter 550 is sized substantially similar to the perimeter of the cavity 720. However, in the exemplary embodiments where at least a portion of the cutter table 120 is not within the cavity 720, the indenter 550 can be dimensioned such that the perimeter of the indenter 550 is greater than the perimeter of the cavity 720. The indenter 550 is oriented so that the first end 650 makes contact with the cutter 100. Thus, in this embodiment, the PDC layer of the indenter 550 makes contact with the PDC layer, or cutter table 120, of the cutter 100. The load 580 is applied to the second end 652, which transmits the load 580 onto the cutter 100. Although a dome shaped indenter 550 is used in these exemplary embodiments, other exemplary embodiments can use indenters having other shapes. Also, the second end 652 can be formed into other non-planar shapes without departing from the scope and spirit of the exemplary embodiments.

The acoustic sensor 570 is a piezoelectric sensor that is positioned along the coupling portion 730 of the cutter holder 510. However, the acoustic sensor 570 can be any other device type known to people having ordinary skill in the art, wherein the device is capable of detecting acoustic transmissions. The acoustic sensor 570 detects elastic wave signals formed in the cutter 100, which then converts the elastic waves signal to a voltage signal so that the data can be recorded and subsequently analyzed. In certain exemplary embodiments, the lubricant 620 is placed at the contact area between the coupling portion 730 and the acoustic sensor 570. As previously mentioned, the lubricant 620 improves detection of elastic wave transmission from the cutter 100 to the acoustic sensor 570. According to some alternative exemplary embodiments, the acoustic sensor 570 is sized so that it is capable of being placed on the arcuate portion of the side surface 716. The acoustic sensor 570 is communicably coupled to the data recorder 590 so that the voltage signal derived from the elastic waves occurring within the cutter 100 can be stored and subsequently analyzed. The acoustic sensor 570 is coupled to the data recorder 590 using a cable 592; however, according to other exemplary embodiments, the acoustic sensor 570 can be communicably coupled to the data recorder 590 wirelessly using wireless technology including, but not limited to, infrared and radio frequency.

The data recorder 590 records the data sent from the acoustic sensor 570 and stores the data therein. In certain exemplary embodiments, the apparatus (not shown), or machine, delivering the load 580 also is coupled to the data recorder 590 using a cable 582; however, according to other exemplary embodiments, the apparatus delivering the load 580 can be communicably coupled to the data recorder 590 wirelessly using wireless technology including, but not limited to, infrared and radio frequency. The data recorder 590 also processes and analyzes the data that it receives. Although the data recorder 590 records, stores, processes, and analyzes the data, the data recorder 590 can receive the data, process the data, and analyze the data without storing the data according to some exemplary embodiments. Alternatively, in other exemplary embodiments, the data recorder 590 can store the data but not process or analyze the data. In some exemplary embodiments, an additional device (not shown) is used to process and analyze the data.

FIG. 10 shows a schematic block diagram of a data recorder 590 of FIG. 5 in accordance with an exemplary embodiment. Referring to FIGS. 5 and 10, the data recorder 590 is a computer system. The data recorder 590 includes a storage medium 1040, a user interface 1030, a processor 1020, and a display 1010.

The storage medium 1040 receives information from the acoustic sensor 570 (FIG. 5) and records the information therein. The storage medium 1040 is a hard drive according to one exemplary embodiment. However, according to other exemplary embodiments, the storage medium 1040 includes at least one of a hard drive, a portable hard drive, a USB drive, a DVD, a CD, or any other device capable of storing data and/or software. In some exemplary embodiments, the storage medium 1040 also includes a software for providing instructions on how to process the information, or data, received from the acoustic sensor 570 (FIG. 5).

The user interface 1030 allows a user to interface with the data recorder 590 and provide instructions for operating the data recorder 590. According to some exemplary embodiments, the user interface includes a keyboard. However, according to other exemplary embodiments, the user interface includes at least one of a keyboard, a mouse, a touch screen which can be part of the display 1010, or any other user interface known to people having ordinary skill in the art.

The processor 1020 is capable of receiving instructions from the user interface 1030, accessing information stored within the storage medium 1040, sending information to the storage medium 1040, and sending information to the display 1010. In some exemplary embodiments, the processor 1020 accesses the software that resides within the storage medium 1040 and executes the set of instructions provided by the software. A more detailed description of these instructions are provided further below. In some exemplary embodiments, the processor 1020 includes processor engines 2200, which are described in further detail below in conjunction with FIGS. 16, 17, 18, and 22.

The display 1010 receives information from the processor and communicates this information to the user. According to one exemplary embodiment, the display 1010 includes a monitor, or screen. However, according to other exemplary embodiments, the display 1010 includes at least one of a screen, a touch screen, a printer, or any other device capable of communicating information to the user.

Although not illustrated in FIG. 10, the data recorder 590 can be communicably coupled, either wired or wirelessly, to an internal network, wherein the software and/or data from the acoustic sensor 570 (FIG. 5) is stored in a central server (not shown). Additionally, according to some alternative exemplary embodiments, the data recorder 590 can be communicably coupled, either wired or wirelessly, to a modem (not shown), wherein the modem is communicably coupled to the world wide web. In certain alternative exemplary embodiments, the software and/or data from the acoustic sensor 570 (FIG. 5) is stored in a remote location that is accessible via the world wide web.

FIG. 8 shows a perspective view of the acoustic emission testing device 505 of FIG. 5 with the indenter 550 being removed from the cutter holder 510 in accordance with an exemplary embodiment of the present invention. Referring to FIG. 8, the cutter 100 is fully inserted within the cavity 720 of the cutter holder 510. As shown, the diameter of the cutter 100 is less than the diameter of the cavity 720, thereby forming the air gaps 610. Also, the PDC layer, or the cutter table 120, is oriented within the cavity 720 so that the PCD layer faces towards the first surface 712. The indenter 550 is removed from the cavity 720 to further illustrate some features of the indenter 550. According to this exemplary embodiment, the indenter 550 includes a substrate 808 and a hard surface 810, which is formed or coupled to the top of the substrate 808. In the exemplary embodiment, the hard surface 810 is formed from PCD, but alternative exemplary embodiments can have the hard surface 810 fabricated from other hard or superhard materials, such as PCBN, without departing from the scope and spirit of the exemplary embodiment. Although indenter 550 has a dome shaped hard surface 810, the hard surface 810 can be planar or any other shape known to people having ordinary skill in the art. As seen, the indenter 550 has a diameter substantially similar to the diameter of the cavity 720, according to this exemplary embodiment.

In an alternative embodiment, the indenter 550 is positioned within the cavity 720 having the hard surface 810 facing towards the first surface 712. The cutter 100 to be tested is positioned on top of the indenter 550 with the cutter table 120 contacting the hard surface 810. The load 580 is applied downward on the back face of the substrate 110 of the test cutter 100. Acoustic emissions of cracks initiated and/or propagated in the test cutter 100 is transmitted through the indenter 550 and to the acoustic sensor 570. In this alternative exemplary embodiment, the cutter holder 510 is optional.

FIG. 9 shows a perspective view of an acoustic emission testing system 900 in accordance with an alternative exemplary embodiment of the present invention. Referring to FIG. 9, the acoustic emission testing system 900 includes an acoustic emission testing device 905 communicably coupled to the data recorder 507. The acoustic emission testing device 905 is similar to the acoustic emission testing device 505 of FIG. 5, except that the acoustic sensor 570 is directly coupled to the cutter 100 and the cutter holder 510 of FIG. 5 is removed. The cutter 100, the indenter 550, the load 580, the acoustic sensor 570, and the data recorder 590 have been previously described with respect to FIGS. 5, 6, 7, 8, and 10. Also, the lubricant 620 (FIG. 6) is placed between the acoustic sensor 570 and the cutter 100 according to some exemplary embodiments.

The operation of the acoustic emission testing system 500 is described while referring to FIGS. 5-8. The cutter 100, or hard or superhard material, to be tested is placed within the cavity 720 of the cutter holder 510. To improve the elastic wave transmission across the contacting surfaces between the base, or bottom surface, of the cutter 100 and the base of the cavity 720, a mineral oil based gel 620 is used between the bottom surface of the cutter 100 and the base of the cavity 720. The acoustic sensor 570 is positioned against the coupling portion 730 of the cutter holder 510 to detect the elastic waves generated within the cutter 100. To improve the elastic wave transmission across the contacting surfaces between the acoustic sensor 570 and the coupling portion 730, the mineral oil based gel 620 also is used between the acoustic sensor 570 and the coupling portion 730. The indenter 550 is placed on top of the PCD layer 120 of the cutter 100 and is pushed against this PCD layer 120 using the load 580. The load 580 is provided on the indenter 550 using a 100 kilonewton 8500 series Instron machine. This machine (not shown) is capable of controlling the amount of load that is exerted on the indenter 550. The machine is hooked up to the data recorder 590 so that load versus time is measured. Although one example of a machine capable of providing the load 580 is disclosed, any system capable of providing a measurable load to the indenter 550 is in the scope of exemplary embodiments for this invention. For example, the machine or apparatus for delivering the measurable load 580 can range from a handheld hammer to a fully instrumented impact machine or to a load controlled hydraulic machine for steady ramp or cyclic loading histories.

The load 580 is applied onto the indenter 550 and increased at a constant rate to a desired load level. Once reaching the desired load level, the load level is maintained for a desired period of time, which can range from a few seconds to several minutes, and then ramped down at a faster rate than the ramp up rate. Each time a new crack forms or an existing crack grows within the top diamond layer 130, a certain amount of elastic energy is released almost instantaneously in the form of a train of elastic waves travelling through the PCD layer 120, the substrate 110, and the cutter holder 510. The acoustic sensor 570 detects these elastic waves and converts the received signals into a voltage signal. The acoustic sensor 570 is communicably coupled to the data recorder 590 so that acoustic emissions, or data, are recorded against time. These acoustic emissions include background noise and acoustic events. Hence, since the acoustic emissions history and the loading history is recorded onto the data recorder 590, one can determine at what load 580 certain acoustic events occurred. An acoustic event is an event where a new crack forms or when an existing crack grows in the PDC layer 120. According to one exemplary embodiment, the acoustic sensor 570 provides data to the data recorder 590 at about 5,000 data points per second; however, the data points per second can be increased or decreased without departing from the scope and spirit of the exemplary embodiment.

FIG. 11 shows a graphical cutter acoustic emission and loading representation 1100 for a cutter experiencing a load of up to about two kilonewtons in accordance with an exemplary embodiment of the present invention. Referring to FIG. 11, the cutter acoustic emission and loading representation 1100 includes a time axis 1110, a load axis 1120, and an acoustic emissions axis 1130. The time axis 1110 is represented by an x-axis and is provided with units in the seconds times 5,000. Thus, to obtain the time period in seconds, the numerical value in the time axis 1110 is to be divided by 5,000. The time axis 1110 can also be read as energy being delivered to the sample. In other words, as more time passes, more total energy is exerted on the cutter or test sample. The load axis 1120 is represented by a y-axis and is provided with units in the kilonewtons. The acoustic emissions axis 1130 also is represented by the y-axis and is provided with units in the millivolts times ten. Thus, to obtain the voltage in millivolts, the numerical value in the acoustic emissions axis 1130 is to be divided by ten. A load curve 1140 and an acoustic emissions curve 1160 are both illustrated on the cutter acoustic emission and loading representation 1100. According to the load curve 1140, the load was increased from zero kilonewtons to two kilonewtons at a constant rate 1142, or ramp up rate. The load was held at a peak load level 1143, or two kilonewtons in this example, for a period of time and then ramped down at a ramp down rate 1144, which is faster than the ramp up rate 1142. The acoustic emissions curve 1160 represents the recorded signal from the acoustic sensor. According to the acoustic emissions curve 1160, the only acoustic emissions recorded is a background noise 1162. There were no acoustic events that were detected. Also, as the load increases, the background noise 1162 also increases.

FIG. 12 shows a graphical cutter acoustic emission and loading representation 1200 for a cutter experiencing a load of up to about five kilonewtons in accordance with an exemplary embodiment of the present invention. Referring to FIG. 12, the cutter acoustic emission and loading representation 1200 includes a time axis 1210, a load axis 1220, and an acoustic emissions axis 1230. The time axis 1210 is represented by an x-axis and is provided with units in the seconds times 5,000. Thus, to obtain the time period in seconds, the numerical value in the time axis 1210 is to be divided by 5,000. The time axis 1210 can also be read as energy being delivered to the sample. In other words, as more time passes, more total energy is exerted on the cutter or test sample. The load axis 1220 is represented by a y-axis and is provided with units in the kilonewtons. The acoustic emissions axis 1230 also is represented by the y-axis and is provided with units in the millivolts times ten. Thus, to obtain the voltage in millivolts, the numerical value in the acoustic emissions axis 1230 is to be divided by ten. A load curve 1240 and an acoustic emissions curve 1260 are both illustrated on the cutter acoustic emission and loading representation 1200. According to the load curve 1240, the load was increased from zero kilonewtons to five kilonewtons at a constant rate 1242, or ramp up rate. The load was held at a peak load level 1243, or five kilonewtons in this example, for a period of time and then ramped down at a ramp down rate 1244, which is faster than the ramp up rate 1242. The acoustic emissions curve 1260 represents the recorded signal from the acoustic sensor. According to the acoustic emissions curve 1260, the only acoustic emissions recorded is a background noise 1262. There were no acoustic events that were detected. Also, as the load increases, the background noise 1262 also increases.

FIG. 13 shows a graphical cutter acoustic emission and loading representation 1300 for a cutter experiencing a load of up to about thirty kilonewtons in accordance with an exemplary embodiment of the present invention. Referring to FIG. 13, the cutter acoustic emission and loading representation 1300 includes a time axis 1310, a load axis 1320, and an acoustic emissions axis 1330. The time axis 1310 is represented by an x-axis and is provided with units in the seconds times 5,000. Thus, to obtain the time period in seconds, the numerical value in the time axis 1310 is to be divided by 5,000. The time axis 1310 can also be read as energy being delivered to the sample. In other words, as more time passes, more total energy is exerted on the sample. The load axis 1320 is represented by a y-axis and is provided with units in the kilonewtons. The acoustic emissions axis 1330 also is represented by the y-axis and is provided with units in the millivolts times ten. Thus, to obtain the voltage in millivolts, the numerical value in the acoustic emissions axis 1330 is to be divided by ten. A load curve 1340 and an acoustic emissions curve 1360 are both illustrated on the cutter acoustic emission and loading representation 1300. According to the load curve 1340, the load was increased from zero kilonewtons to thirty kilonewtons at a constant rate 1342, or ramp up rate. The load was held at a peak load level 1343, or thirty kilonewtons in this example, for a period of time and then ramped down at a ramp down rate 1344, which is faster than the ramp up rate 1342. The acoustic emissions curve 1360 represents the recorded signal from the acoustic sensor. According to the acoustic emissions curve 1360, the acoustic emissions recorded includes a background noise 1362 and one or more acoustic events 1364. The background noise 1362 makes up the bulk of the data recorded during the test. The acoustic events 1364 are shown as thin vertical lines that significantly extend upwards from the background noise 1362. The height of each acoustic event 1364 above the background noise 1362 is proportional to the amount of elastic energy released by each cracking formation and/or propagation event by means of a calibration constant. Every single acoustic event 1364 lasts on average about fifty milliseconds. According to this exemplary embodiment, the acoustic sensor samples about 5,000 data points per second, which allows detection of these acoustic events 1364. Also, as the load increases, the background noise 1362 also increases. After completing this test, the cutter was visually examined. Although there were no visual signs of any damage on the top PCD surface of the cutter, the acoustic sensor did detect acoustic events occurring within the cutter. Thus, the acoustic sensor is able to detect minimal damage occurring to the cutters once exposed to a load eventhough the damage is not visible.

FIG. 14 shows a graphical cutter acoustic emission and loading representation for a cutter experiencing a load of up to about forty kilonewtons in accordance with an exemplary embodiment of the present invention. The same cutter sample used in the tests represented in FIG. 13 was used in the test represented in FIG. 14. Referring to FIG. 14, the cutter acoustic emission and loading representation 1400 includes a time axis 1410, a load axis 1420, and an acoustic emissions axis 1430. The time axis 1410 is represented by an x-axis and is provided with units in the seconds times 5,000. Thus, to obtain the time period in seconds, the numerical value in the time axis 1410 is to be divided by 5,000. The time axis 1410 can also be read as energy being delivered to the sample. In other words, as more time passes, more total energy is exerted on the sample. The load axis 1420 is represented by a y-axis and is provided with units in the kilonewtons. The acoustic emissions axis 1430 also is represented by the y-axis and is provided with units in the millivolts times ten. Thus, to obtain the voltage in millivolts, the numerical value in the acoustic emissions axis 1430 is to be divided by ten. A load curve 1440 and an acoustic emissions curve 1460 are both illustrated on the cutter acoustic emission and loading representation 1400. According to the load curve 1440, the load was increased from zero kilonewtons to forty kilonewtons at a constant rate 1442, or ramp up rate. The load was held at a peak load level 1443, or forty kilonewtons in this example, for a period of time and then ramped down at a ramp down rate 1444, which is faster than the ramp up rate 1442. The acoustic emissions curve 1460 represents the recorded signal from the acoustic sensor. According to the acoustic emissions curve 1460, the acoustic emissions recorded includes a background noise 1462 and one or more acoustic events 1464. The acoustic events 1464 are shown as vertical lines that significantly extend upwards from the background noise 1462. The height of each acoustic event 1464 above the background noise 1462 is proportional to the amount of elastic energy released by each cracking formation and/or propagation event by means of a calibration constant. As seen in FIG. 14, acoustic events 1464 did not occur within the cutter until the load reached or exceeded the previous load that was exposed to this cutter. For example, this cutter previously experienced loads up to thirty kilonewtons as described in FIG. 13. Thus, new acoustic events 1464 did not arise until the load reached and/or exceeded a threshold 1466, which was about thirty kilonewtons in this example, that was previously applied on to the cutter. Based upon the experiments, it seems that to generate new cracks or to grow existing cracks in the cutter that were formed in a previous test run, a load level equal to or higher than the previous peak load level 1343 is to be applied.

FIG. 15A shows a graphical cutter acoustic emission and loading representation 1500 for a cutter manufacturer #1 cutter sample #1 cutter type experiencing a load of up to about forty-five kilonewtons in accordance with an exemplary embodiment of the present invention. FIG. 15B shows a graphical cutter acoustic emission and loading representation 1550 for a cutter manufacturer #2 cutter sample #2 cutter type experiencing a load of up to about thirty kilonewtons in accordance with an exemplary embodiment of the present invention. Referring to FIGS. 15A and 15B, the cutter acoustic emission and loading representation 1500 includes an acoustic emission curve 1510 showing one or more acoustic events 1520 occurring within the cutter manufacturer #1 cutter sample #1 cutter type, while the cutter acoustic emission and loading representation 1550 includes an acoustic emission curve 1560 showing one or more acoustic events 1570 occurring within the cutter manufacturer #2 cutter sample #2 cutter type. There are significantly more acoustics events 1520 and 1570 occurring within the cutter manufacturer #2 cutter sample #2 cutter type than in the cutter manufacturer #1 cutter sample #1 cutter e. Thus, different cutter types show different acoustic patterns within their respective acoustic emissions curve. Based upon these results, a user can determine which cutter type is tougher than another cutter type and can thereby rank cutters according to their toughness. In this case, the cutter manufacturer #1 cutter sample #1 cutter type is tougher than the cutter manufacturer #2 cutter sample #2 cutter type.

Based upon the experimental results shown in FIGS. 11-15, there are at least several observations that can be made. First, the acoustic sensor is able to detect crack formation and crack growth within the diamond table of the cutter as the indenter is being loaded and is able to send signals that are subsequently analyzable. Second, different cutter types show different acoustic event patterns and allow a user to rank the toughness of the cutter when compared to another cutter. Third, although there can be no visible damage that is detectable on the surface of the PDC table of the cutter after the test, the acoustic sensor is able to detect any non-visible damage occurring to the cutter.

FIG. 16 illustrates a flowchart of a method 1600 for analyzing data points received from the acoustic sensor, wherein the method includes a loop one method 1680 and a loop two method 1690 in accordance with an exemplary embodiment of the present invention. Although certain steps are shown as proceeding in a particular order, the sequence of steps can be varied without departing from the scope and spirit of the exemplary embodiment. Also, although certain functions are performed in one or more steps, the number of steps for performing that function can be increased or decreased without departing from the scope and spirit of the exemplary embodiment.

Referring to FIG. 16, at step 1605, the method 1600 starts. From step 1605, method 1600 proceed to step 1610. At step 1610, one or more minimum threshold values above the background noise to qualify a data point as a possible acoustic event is determined. Upon completion of step 1610, method 1600 proceeds to step 1615 and step 1625, which can occur simultaneously in certain exemplary embodiments. At step 1615, the background points delimiting the outer envelop of the background noise is determined. At step 1625, the possible acoustic event points is determined based upon the one or more threshold values determined at step 1610. Step 1615 and step 1625 are included in the loop one method 1680, which is described in further detail below in conjunction with FIG. 17.

From step 1615, method 1600 proceeds to step 1620. At step 1620, the background points determined at step 1615 are interpolated to produce a background noise function curve. From steps 1620 and 1625, method 1600 proceeds to step 1630. At step 1630, actual acoustic event points are determined using the possible acoustic event points determined at step 1680 and the background noise function curve determined at step 1620. From step 1630, method 1600 proceeds to step 1635. At step 1635, the amplitude and duration of each actual acoustic event point is determined. From step 1635, method 1600 proceeds to step 1640. At step 1640, the area under each acoustic event point is calculated. From step 1640, method 1600 proceeds to step 1645. At step 1645, the cumulative distribution of the areas is compared to the actual test load for each acoustic event point. A user can use this comparison to make a determination as to the relative toughness of one cutter to another cutter. This comparison allows the determination to be made using a quantitative and objective methods. The duration, amplitude, and frequency of the acoustic event points and the corresponding level of energy, or load, delivered to the sample can be correlated directly with the field impact performance of the PCD, or other hard or superhard material, being tested. Method 1600 allows measurement of not only the smallest amount of external work, or load, required to initiate some damage but also allows measurement of the amount of additional work, or load, that has to be done to increase the damage level. After step 1645, method 1600 proceed to step 1650 where method 1600 is stopped.

FIG. 19 shows a graphical cutter acoustic emission representation 1900 for a cutter experiencing a load in accordance with an exemplary embodiment of the present invention. FIG. 20 shows a magnified view of a portion of a graphical cutter acoustic emission representation 2000 for a cutter experiencing a load in accordance with an exemplary embodiment of the present invention. FIG. 21 shows a cumulative distribution representation 2100 for each actual acoustic event in accordance with an exemplary embodiment of the present invention. FIGS. 19-21 depict a majority of the steps illustrated in method 1600 of FIG. 16.

Referring to FIG. 19, the cutter acoustic emission representation 1900 includes a time axis 1910 and an acoustic emissions axis 1930. The time axis 1910 is represented by an x-axis and is provided with units in the seconds times 5,000. Thus, to obtain the time period in seconds, the numerical value in the time axis 1910 is to be divided by 5,000. The acoustic emissions axis 1930 is represented by a y-axis and is provided with units in the millivolts time ten. Thus, to obtain the voltage in millivolts, the numerical value in the acoustic emissions axis 1930 is to be divided by ten. An acoustic emissions data 1960 is illustrated on the cutter acoustic emission representation 1900. The acoustic emissions data 1960 represents the recorded signal from the acoustic sensor. According to the acoustic emissions data 1960, the acoustic emissions data recorded includes one or more background points 1962 and one or more possible acoustic event points 1964. Referring to FIGS. 16 and 19 and according to step 1615 and step 1625 of FIG. 16, the acoustic emissions data 1960 is sorted to include background points 1962 and possible acoustic event points 1964. The sorting of the acoustic emissions data 1960 is performed using an algorithm that resides within data recorder 590 (FIG. 5) according to one exemplary embodiment. However, the algorithm can be stored in another device in alternative exemplary embodiments or is performed manually. Alternatively, other methods known to people having ordinary skill in the art and having the benefit of the present disclosure can be used to categorize the acoustic emissions data 1960. As shown in FIG. 19, each background point 1962 is marked with a circle and each possible acoustic event point 1964 is marked with a square. There are some points that are not defined as either a background point 1962 or a possible acoustic event point 1964. These markings are for illustrative purposes and is not meant to limit the scope of exemplary embodiments of the present invention.

Referring to FIGS. 16 and 19 and according to step 1620 of FIG. 16, a background noise function curve 1970 is interpolated using the determined background points 1962. According to one exemplary embodiment, the background noise function curve 1970 is interpolated using a fourth degree polynomial; however, other degrees of polynomial can be used to interpolate the background points 1962 without departing from the scope and spirit of the exemplary embodiment.

Referring to FIG. 20, a magnified portion of the graphical cutter acoustic emission representation 2000 is presented. According to this figure, each acoustic emissions data 1960, which includes the actual acoustic event points 2010, has a time duration 2020 that it occurs in. Additionally, each actual acoustic event point 2010, has an amplitude 2030 that is measured vertically from the background noise function curve 1970 to the position where the actual acoustic event point 2010 lies. Referring to FIGS. 16 and 20 and according to step 1635 of FIG. 16, the amplitude 2030 and the time duration 2020 of the actual acoustic event point 2010 is calculated. Once the amplitude 2030 and the time duration 2020 is determined, the area 2040 under each actual acoustic event point 2010 is calculated by multiplying the amplitude 2030 to the time duration 2020. This step is accomplished in step 1640 of FIG. 16. According to some of the exemplary embodiments, the units for the area 2040 is millivolt times seconds times 5,000; however, other units can be used without departing from the scope and spirit of the exemplary embodiment.

Referring to FIG. 21, a cumulative distribution representation 2100 for each actual acoustic event is presented. According to this figure, the cumulative distribution representation 2100 includes a load axis 2110 and an acoustic emissions area axis 2130. The load axis 2110 is represented by an x-axis and is provided with units in the kilonewtons. The acoustic emissions area axis 2130 is represented by a y-axis and is provided with units in the millivolts times seconds times fifty thousand. This is the area that is determined that lies under an actual acoustic event point. Thus, to obtain the area in millivolts times seconds, the numerical value in the acoustic emissions area axis 2130 is to be divided by fifty thousand. Referring to FIGS. 16 and 21 and according to step 1645 of FIG. 16, the cumulative distribution of the areas, which is plotted along the acoustic emissions area axis 2130, is compared to the actual test load, which is plotted along the load axis 2110, for each actual acoustic event. The cumulative distribution representation 2100 provides these comparisons for a cutter manufacturer #1 cutter sample #1 cutter plot 2150 and a cutter manufacturer #2 cutter sample #2 cutter plot 2160.

For example, in one of the three cutter manufacturer #1 cutter sample #1 cutter plots 2150, there is an actual acoustic event point at about twenty-eight kilonewtons and at about 3550 millivolt times seconds times 50,000, which is labeled as a Point A 2152. This means that there has been a cumulative area of 3550 millivolt times seconds times 50,000 which has occurred under all previous actual acoustic event points, including the area for the actual acoustic event point that occurred at about a load of about twenty-eight kilonewtons. The next actual acoustic event point, Point B 2154, on that same curve occurs at about 32.5 kilonewtons. The area under that actual acoustic event point is about 650 millivolt times seconds times 50,000, which is not directly shown on the cumulative distribution representation 2100. However, at about 32.5 kilonewtons, there has been a cumulative area of about 4200 millivolt times seconds times 50,000. Thus, about 4200 millivolt times seconds times 50,000 minus about 3550 millivolt times seconds times 50,000 is equal to about 650 millivolt times seconds times 50,000. The harder cutter, or the one that is more intrinsically tougher, provides a curve that has a less cumulative area for a given load. A cutter with a steep curve with a lot of high amplitude actual acoustic event points is less intrinsically tougher than a cutter with a less steep curve and fewer high amplitudes actual acoustic event points. Thus, according to the cumulative distribution representation 2100, a comparison between the cutter manufacturer #1 cutter sample #1 cutter plot 2150 and the cutter manufacturer #2 cutter sample #2 cutter plot 2160 indicates that the cutter manufacturer #1 cutter sample #1 cutter is intrinsically tougher than the cutter manufacturer #2 cutter sample #2 cutter. Also, according to FIG. 21, there are three curves that represent the cutter manufacturer #1 cutter sample #1 cutter plot 2150 and two curves that represent the cutter manufacturer #2 cutter sample #2 cutter plot 2160. These plots 2150 and 2160 illustrate that method 1600 (FIG. 16) has a high resolution so that variabilities within samples of the same group are detectable. The method provided in FIG. 16 provides information to a user for ranking cutter toughnesses amongst other cutters in an objective manner.

FIG. 17 illustrates a detailed flowchart of the loop one method 1680 of FIG. 16 in accordance with an exemplary embodiment of the present invention. Referring to FIG. 17, at step 1705, the loop one method 1680 starts. From step 1705, loop one method 1680 proceeds to step 1710. At step 1710, the first data point is read. Upon completion of step 1710, loop one method 1680 proceeds to step 1715, where the next data point is read. After step 1715, loop one method 1680 proceeds to step 1720. At step 1720, the difference between the two data points is calculated and compared to a first tolerance value that is used to define an acoustic event. According to one exemplary embodiment, the first tolerance value is about 0.5 millivolts. However, the first tolerance value can be higher or lower in other exemplary embodiments. If the difference between the two data points is not less than the first tolerance value, loop one method 1680 proceeds to step 1725. At step 1725, the second of the two data points is defined as a possible acoustic event point. From step 1725, loop one method 1680 proceeds to step 1745, where loop one method 1680 determines whether there is another data point. If at step 1745, it is determined that there is not another data point, loop one method 1680 proceeds to step 1750, where the loop one method 1680 stops. However, if at step 1745, it is determined that there is another data point, the loop one method 1680 proceeds back to step 1715.

If at step 1720, it is determined that the difference between the two data points is less than the first tolerance value, the loop one method 1680 proceeds to step 1730. At step 1730, the difference between the two data points is compared to a second tolerance value. According to one exemplary embodiment, the second tolerance value is about 0.01 millivolts. However, the second tolerance value can be higher or lower in other exemplary embodiments. If the difference between the two data points is not less than the second tolerance value, loop one method 1680 proceeds back to step 1715 and the second data point is not defined. However, if the difference between the two data points is less than the second tolerance value, loop one method 1680 proceeds to step 1735.

At step 1735, it is determined whether the difference between the two data points is negative and has been negative for less than “z” times in a row or whether the difference is positive and has been positive for less than “u” times in a row. According to one exemplary embodiment, the “z” is two and the “u” is three. However, either or both the “u” value and the “z” value can be higher or lower in other exemplary embodiments. If it is not true that the difference between the two data points is negative and has been negative for less than “z” times in a row or is positive and has been positive for less than “u” times in a row, then the loop one method 1680 proceeds back to step 1715 and the second data point is not defined. However, if the difference between the two data points is negative and has been negative for less than “z” times in a row or is positive and has been positive for less than “u” times in a row, then the loop one method 1680 proceeds to step 1740.

At step 1740, the second of the two data points is defined as a background boundary point. From step 1740, the loop one method 1680 proceeds to step 1745, where it is determined whether there is another data point. The loop one method 1680 continues until step 1750 is reached pursuant to the steps described above. Thus, the loop one method 1680 provides a method for determining which data points should be defined as a possible acoustic event point, a background boundary point, or not defined as either type of point.

FIG. 18 illustrates a detailed flowchart of the loop two method 1690 of FIG. 16 in accordance with an exemplary embodiment of the present invention. Referring to FIG. 18, at step 1805, the loop two method 1690 starts. From step 1805, loop two method 1690 proceeds to step 1810. At step 1810, a background noise function curve is created using the background boundary points. Upon completion of step 1810, loop two method 1690 proceeds to step 1815, where the first possible acoustic event point is read. After step 1815, loop two method 1690 proceeds to step 1820. At step 1820, the difference between the possible acoustic event point and the background noise function curve is calculated and determined whether this difference is greater than a third tolerance value that is used to define an actual acoustic event point. According to one exemplary embodiment, the third tolerance value is about 0.08 millivolts. However, the third tolerance value can be higher or lower in other exemplary embodiments. If the difference between the possible acoustic event point and the background noise function curve is not greater than the third tolerance value, loop two method 1690 proceeds to step 1825. At step 1825, the next possible acoustic event point is read and the loop two method 1690 proceeds back to step 1820. However, if the difference between the possible acoustic event point and the background noise function curve is greater than the third tolerance value, loop two method 1690 proceeds to step 1830.

At step 1830, the amplitude, the duration, and the area between the actual acoustic event point and the background noise function curve are calculated From step 1830, the loop two method 1690 proceeds to step 1840. At step 1840, it is determined whether there is another possible acoustic event point. If there is another possible acoustic event point, the loop two method 1690 proceeds back to step 1825, where the loop two method 1690 continues. However, at step 1840, if there is not another possible acoustic event point, the loop two method 1690 proceeds to step 1845, where the loop two method 1690 stops. Thus, the loop two method 1690 provides a method for determining which data points should be defined as an actual acoustic event point and then calculates the area for each defined acoustic event point.

FIG. 22 illustrates a block diagram of the processor 1020 of FIG. 10 in accordance with an exemplary embodiment. As previously mentioned, the method for performing one or more steps illustrated in FIGS. 16-18 is performed within the processor 1020. However, in certain other exemplary embodiments, these methods are performed manually or a combination of manually and within a processor. The processor 1020 is located within the data recorder 590, or a computer system. Although one processor 1020 is shown, multiple processors can be used without departing from the scope and spirit of the exemplary embodiments. Processor 1020 includes one or more processor engines 2200.

The processor engines 2200 include an acoustic data gathering engine 2210, a background points determination engine 2220, a possible acoustic event points determination engine 2230, a background noise function curve interpolation engine 2240, an actual acoustic event points determination engine 2250, an actual acoustic event area calculation engine 2260, and a cumulative area and load curve engine 2270. Although seven engines are included within the processor engines 2200, the number of engines can be greater or fewer in other exemplary embodiments. Additionally, one or more of these previously mentioned processor engines 2200 can be combined into fewer processor engines 2200 or separated into additional processor engines 2200 without departing from the scope and spirit of the exemplary embodiments.

The acoustic data gathering engine 2210 gathers data from at least the acoustic sensor, which includes background points and possible acoustic event points. The acoustic data gathering engine 2210 also gathers data from the load, in some exemplary embodiments, so that corresponding background points and possible acoustic event points are related to a given load. The background points determination engine 2220 evaluates the data obtained from the acoustic sensor and determines whether the data point is a background point. The background points determination engine 2220 performs step 1615 of FIG. 16. The possible acoustic event points determination engine 2230 evaluates the data obtained from the acoustic sensor and determines whether the data point is a possible acoustic event point. The possible acoustic event points determination engine 2230 performs step 1625 of FIG. 16. The background points determination engine 2220 and the possible acoustic event points determination engine 2230 run simultaneously with one another, but can run independently from one another in some alternative exemplary embodiments.

The background noise function curve interpolation engine 2240 generates a background noise function curve using the background points that were previously determined. The background noise function curve interpolation engine 2240 performs step 1620 of FIG. 16. The actual acoustic event points determination engine 2250 determines actual acoustic event points using the possible acoustic event points that were previously determined and the background noise function curve. The actual acoustic event points determination engine 2250 performs step 1630 of FIG. 16. Once the actual acoustic event points are determined, the actual acoustic event area calculation engine 2260 determines the area formed between the actual acoustic event point and the background noise function curve. The actual acoustic event area calculation engine 2260 performs step 1635 and step 1640 of FIG. 16. The cumulative area and load curve engine 2270 compares the cumulative distribution of the areas to the actual test load for each actual acoustic event point. The cumulative area and load curve engine 2270 performs step 1645 of FIG. 16. Although the processor engines 2200 are located in the processor 1020 in some exemplary embodiments, the processor engines 2200 can reside in a storage medium including, but not limited to, one or more hard drives, a USB drive, a compact disc, a digital video disc, or any other storage device known or not yet known to people having ordinary skill in the art.

Although processor engines 2200 are described in the exemplary embodiments, the instructions for determining the toughness of the cutter can be provided in a software that resides within the storage medium 1040 (FIG. 10). The software includes modules and/or code that are similar to the processor engines 2200 described above.

FIG. 23 shows a rock sample 2300 that is testable within the acoustic emission testing systems 500 and 900 of FIGS. 5 and 9, respectively, in lieu of the cutter 100 of FIG. 1 in accordance with an exemplary embodiment. Referring to FIGS. 5, 6, 9, and 23, the rock sample 2300 replaces the cutter 100 in the acoustic emission testing system 500 or the acoustic emission testing system 900. The testing method and analysis of the results are similar to those methods and analysis described above and provides information relating to the unconfined compressive strength and/or toughness of the sample rock 2300.

The sample rock 2300 is cylindrically shaped, which is similar to the cutter 100. The rock sample includes a first planar surface 2310 at one end of the rock sample 2300, a second planar surface 2320 at an opposing end of the rock sample, and a circumferential surface 2330 extending from the first surface 2310 to the second surface 2320. However, in alternative exemplary embodiments, the sample rock 2300 is shaped in other geometric or non-geometric shapes, such as cube-shaped. In certain exemplary embodiments, the shape of the sample rock 2300 is a repeatable shape such that multiple rock samples 2300 are foamed with a substantially similar shape; thereby allowing the test results to be comparable.

FIG. 24 shows the acoustic emission testing device 505 of FIG. 5 inserted within a pressurizable chamber 2410 in accordance with an exemplary embodiment. The pressure within the pressurizable chamber 2410 is variable in a controllable and measurable manner. The pressure within the pressurizable chamber 2410 is variable from zero psi to about 40000 psi in some exemplary embodiments; however, the range of pressures can be higher or lower in other exemplary embodiments. In this exemplary embodiments, other components, including the sensor 570 and the indenter 550, are capable of withstanding the pressures formed within the pressurizable chamber 2410. According to these exemplary embodiments, the rock confined compressive strength and toughness are measurable at different levels of hydrostatic pressures, thereby providing vital information of the rock properties at different depths below the earth surface. The information collected is usable to improve the knowledge of rock failing mechanisms and also lead to new theories and rock solid mechanic models. The information collected also is usable to confirm other known theories not yet proven. Although the pressurizable chamber 2410 is one method for testing the hard or superhard material 100, such as the rock sample 2300, under pressure, other mechanisms for providing pressures on the hard or superhard material 100 can be used, such as using high strength binding rings assembled together and around the hard or superhard material 100, in alternative exemplary embodiments.

The knowledge of the UCS and the toughness of the rock samples 2300 are usable by designers to create new and innovative bit designs having superior performance and/or to develop a new bit design procedure which incorporates the UCS value and the K_(1C) value. The information obtained from the rock samples 2300 is usable to calibrate geoscience and/or geomechanics software and tools.

Although some exemplary embodiments of the invention have been described, alternative exemplary embodiments include the use of heating the hard or superhard material 100. This heating of the hard or superhard material 100 occurs at either or a combination of before, during, and/or after the application of the load onto the hard or superhard material 100. The heat is supplied in any one of a number of ways known to people having ordinary skill in the art, which include, but is not limited to, flame, laser, infrared, and/or heated liquid.

Although each exemplary embodiment has been described in detail, it is to be construed that any features and modifications that are applicable to one embodiment are also applicable to the other embodiments. Furthermore, although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons of ordinary skill in the art upon reference to the description of the exemplary embodiments. It should be appreciated by those of ordinary skill in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures or methods for carrying out the same purposes of the invention. It should also be realized by those of ordinary skill in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the scope of the invention. 

1. An acoustic emission testing device, comprising: a rock sample comprising a first surface; an acoustic sensor communicably coupled to the rock sample; an indenter releasably coupled to the first surface, the indenter being tougher than the rock sample; and a load exerted onto the indenter, the indenter transferring the load onto the first surface, wherein the load is increased to a peak load at a ramp up rate, the peak load is held for a time period, and the load is decreased at a ramp down rate, and wherein the acoustic sensor senses acoustic events occurring within the rock sample.
 2. The acoustic emission testing device of claim 1, wherein the ramp down rate is greater than the ramp up rate.
 3. The acoustic emission testing device of claim 1, wherein the acoustic sensor is coupled to the rock sample.
 4. The acoustic emission testing device of claim 3, further comprising a lubricant positioned between the acoustic sensor and the rock sample.
 5. The acoustic emission testing device of claim 1, further comprising a testing sample holder comprising a cavity therein, wherein the rock sample is positioned within the cavity, and wherein the acoustic sensor is coupled to the testing sample holder.
 6. The acoustic emission testing device of claim 5, wherein the diameter of the cavity is greater than the diameter of the rock sample, thereby forming an air gap between the outer surface of the cavity and the outer surface of the rock sample.
 7. The acoustic emission testing device of claim 6, further comprising a lubricant positioned within the air gap, the lubricant contacting the outer surface of the cavity, the outer surface of the rock sample, and at least a portion of the air gap therebetween.
 8. The acoustic emission testing device of claim 1, wherein the indenter comprises a PDC end, the PDC end contacting the first surface of the rock sample.
 9. The acoustic emission testing device of claim 1, wherein the indenter comprises a cobalt concentration that ranges from about six percent to about twenty percent.
 10. The acoustic emission testing device of claim 1, wherein the indenter comprises a first end, the first end contacting the rock sample, the first end being dome-shaped.
 11. An acoustic emission testing system, comprising: an acoustic emission testing device comprising: a rock sample comprising a first surface; an acoustic sensor communicably coupled to the rock sample; an indenter releasably coupled to the first surface, the indenter being tougher than the rock sample; and a load exerted onto the indenter, the indenter transferring the load onto the first surface; and a data recorder communicably coupled to the acoustic emission testing device, the data recorder receiving data from the acoustic emission testing device, wherein the load is increased to a peak load at a ramp up rate, the peak load is held for a time period, and the load is decreased at a ramp down rate, and wherein the acoustic sensor senses acoustic events occurring within the rock sample.
 12. The acoustic emission testing system of claim 11, wherein the ramp down rate is greater than the ramp up rate.
 13. The acoustic emission testing system of claim 11, wherein the acoustic sensor is coupled to the rock sample.
 14. The acoustic emission testing system of claim 11, further comprising a testing sample holder comprising a cavity therein, wherein the rock sample is positioned within the cavity, and wherein the acoustic sensor is coupled to the testing sample holder.
 15. The acoustic emission testing system of claim 11, wherein the indenter comprises a first end, the first end contacting the rock sample, the first end comprising a cobalt concentration that ranges from about six percent to about twenty percent.
 16. The acoustic emission testing system of claim 11, wherein the rock sample is subjected under a pressure.
 17. A method for determining the toughness of a rock sample, comprising: providing an acoustic emission system, the acoustic emission testing system comprising: an acoustic emission testing device, comprising: a rock sample comprising a first surface; an acoustic sensor communicably coupled to the rock sample; an indenter releasably coupled to the first surface, the indenter being tougher than the rock sample; and a load exerted onto the indenter, the indenter transferring the load onto the first surface; and a data recorder communicably coupled to the acoustic emission testing device, the data recorder receiving data from the acoustic emission testing device, applying the load onto the indenter, the indenter transferring the load onto the rock sample; obtaining data from the acoustic emission device; detecting acoustic events occurring within the rock sample; and objectively calculating the toughness of the rock sample.
 18. The method of claim 17, wherein applying the load onto the indenter comprises: increasing the load to a peak load at a ramp up rate; holding the peak load for a time period; and decreasing the load at a ramp down rate.
 19. The method of claim 18, wherein the ramp down rate is greater than the ramp up rate.
 20. The method of claim 17, wherein obtaining data from the acoustic emission testing device comprises obtaining data from the acoustic sensor and the load.
 21. The method of claim 17, wherein the acoustic sensor is coupled to the rock sample.
 22. The method of claim 17, wherein the acoustic emission testing device further comprises a testing sample holder comprising a cavity therein, wherein the rock sample is positioned within the cavity, and wherein the acoustic sensor is coupled to the testing sample holder.
 23. The method of claim 17, further comprising heating the rock sample.
 24. The method of claim 17, further comprising pressurizing the rock sample.
 25. A computer-implemented method for determining the toughness of a rock sample, the method comprising the steps of: gathering by an acoustic data gathering engine to gather acoustic data from an acoustic sensor when a load is subjected onto a rock sample, the acoustic sensor being communicably coupled to the rock sample; determining by a background points determination engine to determine one or more background points; determining by a possible acoustic event points determination engine to determine one or more possible acoustic event point; interpolating by a background noise function curve interpolation engine to interpolate a background noise function curve using the background points; determining by an actual acoustic event points determination engine to determine one or more actual acoustic event point using the possible acoustic event point and the background noise function curve; and calculating by an actual acoustic event area calculation engine to calculate an acoustic event area bounded between the actual acoustic event point and the background noise function curve.
 26. The computer-implemented method of claim 25, wherein determining by a background points determination engine and determining by a possible acoustic event points determination engine are performed concurrently.
 27. The computer-implemented method of claim 26, wherein a background point is determined when the difference between two sequential data points is less than a first threshold and wherein a possible acoustic event point is determined when the difference between two sequential data points is greater than the first threshold.
 28. The computer-implemented method of claim 26, wherein a background point is determined when the difference between two sequential data points is less than a second threshold and wherein a possible acoustic event point is determined when the difference between two sequential data points is greater than a first threshold.
 29. The computer-implemented method of claim 26, wherein a background point is determined when the difference between two sequential data points is less than a second threshold and is negative and has been negative for less than “z” times in a row or when the difference between two sequential data points is less than a second threshold and is positive and has been positive for less than “u” times in a row and wherein a possible acoustic event point is determined when the difference between two sequential data points is greater than a first threshold.
 30. The computer-implemented method of claim 25, wherein an actual acoustic event point is determined when the difference between a possible acoustic event point and the background noise function curve is greater than a third threshold.
 31. The computer-implemented method of claim 25, wherein the each acoustic event area is calculated by multiplying an amplitude of each of the actual acoustic event points from the background noise function curve to a respective time duration of each of the actual acoustic event point.
 32. The computer-implemented method of claim 25, further comprising generating by a cumulative area and load curve engine to generate a cumulative area and load curve using a cumulative area bounded between the actual acoustic event point and the background noise function curve for each actual acoustic event point.
 33. The computer-implemented method of claim 32, wherein the cumulative area and load curve is generated by plotting each actual acoustic event point using the load for the corresponding actual acoustic point and a cumulative area for the corresponding actual point, wherein the cumulative area comprises a total area under the corresponding actual acoustic point and under all previous actual acoustic points.
 34. The computer-implemented method of claim 32, wherein a user objectively determines a toughness for the rock sample using the cumulative area and load curve.
 35. The computer-implemented method of claim 25, further comprising pressurizing the rock sample. 